I have an unknown 2D numpy array like the following:
a = np.array([
[1, 2],
[0, 2],
])
I want to use the elements of the array as an index to another array b to produce the following effect:
b = np.random.randn(5, 5)
c = b[[1, 2], [0, 2]]
How can I use the variable a to replace the hardcoded values in the index?
Using the following code did not work:
b = np.random.randn(5, 5)
c = [*a]
As the * expression is used in an index.
Just change the outer layer of a to a tuple to trigger advanced indexing: b[tuple(a)].
This is pretty much how the index syntax of b[[1, 2], [0, 2]] is interpreted; the elements are changed to NumPy arrays and are put into a tuple.
I don't know if I got it but, try using a list for the index instead of an np array:
import numpy as np
a = [
[1, 2],
[0, 2]
]
b = np.random.randn(5, 5)
c = b[a]
arr[tuple(not_a_tuple)] to arr[np.array(not_a_tuple)], which does something different. This code currently prints a FutureWarning that suggests you write arr[tuple(not_a_tuple)] for future versions.
aalways equal to2?